The present invention relates to a pressure relief valve arrangement for a pyrotechnic gas generator in which the generator includes a housing enclosing a combustion chamber having a pyrotechnic propellant charge disposed therein, with control nozzles disposed in the housing and communicating with the exterior of the housing, gas channels connecting the combustion chamber with the nozzles, valve devices for opening and closing the gas channels, and control means for actuating the valve devices.
Pyrotechnic gas generators are useful for, among other things, the purpose of guiding missiles or for steering projectiles or missiles in their final phase of flight. In these devices, a propellant charge is converted into a gas in a combustion chamber, with the gas being conducted to control nozzles if a steering correction is required. Operation of the gas generator suitable for control purposes is possible only at constant pressure conditions within the combustion chamber, so that pressure peaks, in particular, must be avoided.
Attempts have been made to reduce such pressure peaks by means of mechanical pressure relief valves which are composed essentially of a spring-mass system. However, under the high stresses encountered in practice, mechanical pressure relief values require such a large amount of space that they can no longer be disposed in the immediate vicinity of the combustion chamber, particularly in final phase guided missiles. Moreover, due to the relatively great time constant of the spring-mass system, mechanical pressure relief valves exhibit poor response behavior which does not meet requirements in practice. Finally, the opening and closing behavior of conventional mechanical pressure relief valves includes tolerances that are too high and excludes the use of such pressure relief valves for precision guidance.
A further drawback is that the response pressure, which corresponds to the combustion chamber pressure, of such pressure relief valves is fixed and cannot be set to a variable desired pressure as a function of the temperature of the gas generator propellant charge. It is known that the combustion behavior of a propellant charge changes as a function of the existing propellant charge temperature. With a fixedly set combustion chamber pressure, the propellant charge will burn faster, for example at a propellant charge temperature of +65.degree. C., so that the combustion time of the propellant charge is shortened and guided missiles can no longer be controlled in the final phase of their flight. However, with the same setting of the combustion chamber pressure and a lower propellant charge temperature of, for example -40.degree. C., the resulting combustion speed is lower so that, due to the insufficiently produced gas mass stream, the thrust for transverse acceleration of the missile is insufficient.